Display the sentence and give five seconds of quiet think-time before any hands go up. Take three hands-up answers, not open call-outs. Don't confirm right or wrong yet — hold the reveal for Watch and Notice.

Each beam: name the opposite move aloud, then substitute the value so the class sees it level. Take one or two hands-up predictions before each reveal.

□ + 5 = 12: 5 added, so take 5 off 12, box is 7.

□ − 3 = 4: 3 taken off, so add 3 back, put 4 and 3 on the other pan so the box levels at 7. Watch pupils who guess 1, box is bigger than 4 here.

9 = □ + 2: box jumped to the right, same opposite move — 9 − 2, box is 7.

6 + □ = 15: box in the middle now — 15 − 6, box is 9.

12 = 5 + □: the take-away shape the challenge uses — box fills the gap between 5 and 12, box is 7.

□ + 3 = 4 + 6: two numbers on the far side — add them first (4 + 6 = 10), then find the box, box is 7.

Talk this one through together — pupils take turns at the board and the class agrees or corrects out loud.

A pupil sets the box on the beam for □ + 4 = 11 until it levels, then reads the box value. Put the value back into the sentence aloud (4 add 4 is 8… no, we need 11, try again) so the class hears the checking habit. Talk through the other three as number sentences only (the pinned beam cannot show take-away). The □ − 2 = 6 one is the trap: the box must be bigger than 6, not smaller.

Before anyone touches the interactive, teach the twin-box case once on the board.

□ + □ = 16: both boxes hold the same number, so split 16 into two equal parts, 8 and 8. Write 8 + 8 = 16 and read it back. Slip to watch: pupils who say 16 (one box takes the whole total) or 15 (counting on by one twice).

Then run the challenge briskly, pupils take turns, class confirms each Check. 20 = 13 + □ is the take-away shape from Watch and Notice, ask what fills the gap between 13 and 20. Twin-box item should now echo the board demo. Last one: add the far side first (5 + 9 = 14) before touching the box.